1. Field of the Invention
This invention relates to a process for upgrading raw, sulfur-containing petroleum fractions. More particularly, this invention relates to a process for simultaneously desulfurizing and dewaxing an untreated, wide-cut petroleum distillate by contacting same, in the presence of hydrogen, with a catalyst comprising a hydrogenating metal component and faujasite on an amorphous silica/alumina support, with a minimum cracking of feed to gas to obtain a middle distillate product of reduced sulfur and wax content and in an amount at least equal to that in the feed.
2. Description of the Prior Art
Middle distillate petroleum oil fractions boiling in the range of between 300.degree. and 650.degree. F are well known and widely used for various fuels such as kerosene, diesel fuels, domestic heating oils, and jet fuels. However, before these fractions can be used they must be treated to remove sulfur and other impurities along with some of the waxy, normal paraffins normally present therein. The presence of waxy, normal paraffinic materials has an adverse effect on the pour point and cloud point of these various oils and fuel fractions. In the past, sulfur and other impurities have been removed by passing the feed over well known catalysts such as cobalt molybdate on alumina, in the presence of hydrogen, with the wax being subsequently removed via one of the various solvent dewaxing processes employing dewaxing solvents such as autorefrigerants, ketones, aromatics and mixtures thereof.
Catalytic dewaxing has been suggested for removing at least a portion of the wax from middle distillates and thereby lowering the pour point thereof. U.S. Pat. No. 3,294,858 teaches the use of zeolites having a uniform pore size of 5A, such as analcite and chabasite, for catalytically hydrodewaxing middle distillates. However, this patent does not suggest the use of a metal hydrogenating component with the zeolite and, further, the catalysts disclosed therein deactivate very rapidly due to coking or carbon deposition thereon. U.S. Pat. No. 3,876,525 discloses the use of a noble metal supported by decationized or H-mordenite having a silica/alumina ratio of from 10/1 to 15/1 for catalytically dewaxing middle distillate fractions. Unfortunately, a catalyst comprising one or more noble metals on mordenite cannot tolerate raw, unrefined feeds. The feed must first be reduced in metals, sulfur and nitrogen compounds before coming into contact with the mordenite or the mordenite will deactivate very rapidly.
Therefore, notwithstanding the fact that it is now possible to catalytically dewax various petroleum oil fractions, it is still necessary to remove sulfur and other impurities therefrom in order to obtain useful products and in order to have a useful catalyst life. Further, the ever increasing demand for these middle distillate fuel oil fractions has prompted the petroleum industry to find new methods of obtaining same from higher boiling fractions. For example, U.S. Pat. No. 3,268,436 discloses hydrocracking a paraffin wax feed boiling above 650.degree. F down into a jet fuel boiling within the range of 50.degree.]F to 550.degree. F using two catalytic zones, a cracking zone using palladium on faujasite followed by a hydrogenation zone. U.S. Pat. No. 3,617,486 discloses the use of a catalyst comprising either a noble metal or mixed non-noble metals on faujasite to hydrocrack heavy naphtha down into gasoline boiling fractions. U.S. Pat. No. 3,503,871 discloses a hydrocracking catalyst comprising a noble metal on a large pore zeolitic cracking base, including faujasite, for hydrocracking hydrocarbon streams such as naphtha fractions down to obtain products boiling in the gasoline range. This patent discloses that faujasite is a better cracking base than alumina.
It would be a significant improvement to the art if one could obtain middle distillates from raw, wide-cut petroleum fractions and simultaneously lower the pour point and remove the sulfur and other impurities therefrom.